As a conventional electric double layer capacitor comprising an organic electrolytic solution and polarizing electrodes immersed in the solution, there is known an electric double layer capacitor which uses, as the main component of the polarizing electrodes, an active carbon having, on the surface, fine pores formed by a treatment called activation and having a specific surface area of 1,000 m.sup.2 /g or more. In such an electric double layer capacitor, the solute ion dissolved in the organic electrolytic solution is adsorbed inside the fine pores, whereby an electrostatic capacity is exhibited.
In such an electric double layer capacitor having the above constitution, the electrostatic capacity and the dielectric strength are dependent upon the activation method of the active carbon. An electric double layer capacitor using an active carbon subjected to a stream activation method, for example, has an electrostatic capacity of 15 F/cc and a dielectric strength of 3 V; and an electric double layer capacitor using an active carbon subjected to an alkali activation method has an electrostatic capacity of 20 F/cc and a dielectric strength of 2.5 V.
In recent years, higher electrostatic capacity and higher dielectric strength have been desired for electric double layer capacitors and a capacitor having an electrostatic capacity of 30 F/cc or more and a dielectric strength of 3.5 V or more have been sought. However, an electric double layer capacitor using an active carbon, and having such properties has not yet been developed and no process for producing a capacitor having such properties has been reported.
In order to solve the above-mentioned problems, the present invention has been made with an aim of providing a process for producing an electrochemical capacitor which can show an electrostatic capacity and a dielectric strength both higher than those of electric double layer capacitors using an active carbon, by using, as the main component of the polarizing electrodes, a carbon material containing a graphite-like microcrystalline carbon.